The present invention relates to transition metal complex compounds, to polymerisation catalysts based thereon and to their use in the polymerisation and copolymerisation of olefins.
The use of certain transition metal compounds to polymerise 1-olefins for example, ethylene or propylene, is well established in the prior art. The use of Ziegler-Natta catalysts, for example, those catalysts produced by activating titanium halides with organometallic compounds such as triethylaluminium, is fundamental to many commercial processes for manufacturing polyolefins. Over the last twenty or thirty years, advances in the technology have led to the development of Ziegler-Natta catalysts which have such high activities that olefin polymers and copolymers containing very low concentrations of residual catalyst can be produced directly in commercial polymerisation processes. The quantities of residual catalyst remaining in the produced polymer are so small as to render unnecessary their separation and removal for most commercial applications. Such processes can be operated by polmerising the monomers in the gas phase, or in solution or in suspension in a liquid hydrocarbon diluent. Polymerisation of the monomers can be carried out in the gas phase (the xe2x80x9cgas phase processxe2x80x9d), for example by fluidising under polymerisation conditions a bed comprising the target polyolefin powder and particles of the desired catalyst using a fluidising gas stream comprising the gaseous monomer. In the so-called xe2x80x9csolution processxe2x80x9d the (co)polymerisation is conducted by introducing the monomer into a solution or suspension of the catalyst in a liquid hydrocarbon diluent under conditions of temperature and pressure such that the produced polyolefin forms as a solution in the hydrocarbon diluent. In the xe2x80x9cslurry processxe2x80x9d the temperature, pressure and choice of diluent are such that the produced polymer forms as a suspension in the liquid hydrocarbon diluent. These processes are generally operated at relatively low pressures (for example 10-50 bar) and low temperature (for example 50 to 150xc2x0 C.).
In recent years the use of certain metallocene catalysts (for example biscyclopentadienylzirconiumdichloride activated with alumoxane) has provided catalysts with potentially high activity. However, metallocene catalysts of this type suffer from a number of disadvantages, for example, high sensitivity to impurities when used with commercial available monomers, diluents and process gas streams, the need to use large quantities of expensive alumoxanes to achieve high activity, and difficulties in putting the catalyst on to a suitable support.
EP 0924223A discloses a class of catalyst activators, and also provides a long list of catalysts which they may activate. Amongst the catalysts are disclosed two complexes having the formulae: 
where in both cases R4 and R6 are Me, R5 and R7 are 2,4,6-trimethylphenyl, M is Fe, T is II, X is Cl and b is 1. There is no evidence as to whether the compounds were actually made, nor any disclosure as to how the compounds might be made.
An object of the present invention is to provide a novel catalyst suitable for polymerising and oligomerising monomers, for example, olefins such as xcex1-olefins containing from 2 to 20 carbon atoms, and especially for polymerising ethylene alone, propylene alone, or for copolymerising ethylene or propylene with other 1-olefins such as C2-20 xcex1-olefins. A further object of the invention is to provide an improved process for the polymerisation of olefins, especially of ethylene alone or the copolymerisationof ethylene or propylene with higher 1-olefins to provide homopolymers and copolymers having controllable molecular weights. For example, using the catalysts of the present invention there can be made a wide variety of products such as, for example. liquid polyolefins, oligomers, linear xcex1-olefins, branched xcex1-olefins, resinous or tacky polyolefins, solid polyolefins suitable for making flexible film and solid polyolefins having high stiffness.
The present invention provides a complex having the Formula (I): 
wherein M is a transition metal; X represents an atom or group covalently or ionically bonded to M; T is the oxidation state of M; b is the valency of the atom or group X; A1 to A3 are each independently N or P or CR, with the proviso that at least one but no more than two of them are independent, CR; Y1 and Y2 are each independently CRxe2x80x2 or PRxe2x80x2Rxe2x80x3; Z is oxygen or NR5, R5 and R7 and each R, each Rxe2x80x2 and each Rxe2x80x3 are independenty selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl, substituted heterohydrocarbyl or SiR303 where each R30 is independently selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl;
but excluding those complexes having the formulae: 
where in both cases R4 and R6 are Me, R5 and R7 are 2,4,6-trimethylphenyl, M is Fe, T is II, X is Cl and b is 1.